1. Field of the invention
This invention relates to a pressure control.
2. Description of Related Art
In the manufacture of a steel and iron large ovens are used which are charged with coal-coke. The oven drives off volatiles so as to make coke. Coke oven gases evolved through this process are pumped to the by-products plant for processing. A motor or steam turbine has an output shaft which drives an exhauster so as to move collector gas to the by-products plant.
The back pressure in the ovens must be closely controlled and a large number of ovens are connected to each other to form a battery and the battery is connected to a back pressure controller which controls the correct pressure in the battery. In a particular application, a collector main has a gas pressure of eight millimeters back pressure. This is controlled by a valve mounted downstream. On the other side of the valve suction occurs. In prior art control systems, the pressure in the collector main has varied as shown by FIG. 3 which has a number of spikes illustrating the pressure variation which is undesirable. Charging spikes, representing instantaneous pressure fluctuations, were considered by the iron and steel industry to be normal during operations of the charging of coke ovens. With the introduction of increased federal regulations there arose a necessity for better control of gas leakage from the coke ovens. This improved level of control was achieved partially through back pressure control. FIG. 3 was made with a GPE Controls, Inc. Jet Pipe Regulator with proportional reset action. See also U.S. Pat. Nos. 3,695,283, 3,682,191, 3,621,655, 4,644,781, 3,760,840, 4,265,116, 4,276,895, 3,590,840 and 4,874,016.